The present invention is directed to the field of baking equipment and processes and more specifically to an apparatus and method for a continuous product conveyor having a brick-like baking hearth.
A number of oven technologies are known for the production of food substances including pizza, flat breads, traditional breads, and the like. These technologies include common deck ovens, brick ovens, and conveyor ovens, as described below.
Common Deck Ovens
Common deck ovens are predominantly utilized by start-up and low volume independent operations producing food substances with limited resources. This is primarily due to the common deck oven""s lower cost when compared to alternative brick ovens and conveyor ovens. Common deck ovens employ thermostatically controlled cooking chambers of various sizes and dimensions that have interior walls and baking surfaces of various types of metal. Most commonly, these ovens employ a primary heating means of electricity, natural gas, or propane. Baking food substances in a common deck oven usually includes placing the food substance on a heavy pan or similar device. This is necessary because the placement of food substances directly on the metal floor of the cooking chamber can cause sticking, burning, and uneven cooking due to the floor""s metal construction and uneven heat distribution. The baking pan is usually lined with oil that serves to reduce the probability of sticking and to promote browning. The use of a pan also allows the food substance to be easily placed in, manipulated within, and removed from the cooking chamber. The process of pan cooking is generally considered to produce a less crispy, doughy and sometimes soggy crust or product when compared to hearth baking. These beliefs are well-founded as a pan serves as a barrier which hinders the release of steam and moisture during the baking process. The introduction of oil to the pan further inhibits the purging of this moisture and saturates the crust.
In an attempt to produce a more crisp crust from a pan, the prior art has reported removing food substances from the pan near the end of the baking process and placing them directly on the cooking chamber""s metal floor in an attempt to quickly crisp the bottom of the crust via a short period of direct high heat transfer. However, due to the presence of oil in the pan, this practice can result in a slightly foul or sour taste/smell as the oil present in the bottom of the crust can deteriorate when exposed directly to the hot oven floor, thereby imparting the undesirable taste. To obtain a crisp crust on its pan pizza, one national pizza chain places an excessive amount of oil in the pan prior to placing the dough in it. This practice can produce a more crisp crust by causing the bottom portion to fry in the oil during the cooking process, but results in a high fat product.
Pans with holes, screens and similar devices (xe2x80x9cscreensxe2x80x9d) which serve to support food substances expose a greater portion of the food substance to the ambient heat of the oven and allow excess moisture to escape during the baking process thereby enhancing crispness. Employing screens can produce a somewhat effective result when utilized in a faster baking, evenly heated convection oven. However, they produce mixed results when used in conjunction with common deck ovens, as they fail to remedy the inherent uneven heat distribution throughout the oven""s floor. Furthermore the sticking of food substances to such screens is a problem as penetration of the apertures of the screens can result before baking occurs.
Production personnel, bakers, operators of restaurants and production equipment, and individuals familiar with the art (xe2x80x9cbakersxe2x80x9d) who utilize common deck ovens report that the task of producing a consistent product is labor intensive and requires significant training as optimum baking time varies with fluctuating temperatures within the cooking chamber. These fluctuations are the result of bakers repeatedly opening the door to shift food substances cooking on pans or screens to other areas of the cooking chamber floor in an attempt to compensate for uneven heat distribution. This practice results in inconsistent product quality, decreased energy efficiency, and an uncomfortably hot work environment. Also noted was an increased risk of injury due to the intensive interaction with the oven.
When an operation utilizing a common deck oven experiences increased demand, additional deck ovens can be added beside or stacked on top of the existing oven if space allows. The stacking of ovens is considered by some bakers to be a less preferred option as it involves placing the cooking chamber apertures at levels that may not be at an optimum access height.
For various examples of common deck ovens, see U.S. Pat. No. 5,021,635 to Willett; U.S. Pat. No. 4,757,184 to Swanson et al.; and U.S. Pat. No. 4,215,266 to Smith et al., the teachings of all of which are incorporated herein by reference.
Brick Ovens
xe2x80x9cBrickxe2x80x9d ovens fall into a number of categories including: (1) common deck ovens enhanced with a supplemental ceramic, brick, firebrick, stone, baked clay, transite, quarry tile, or other non-metallic materials which serve as a baking surface (xe2x80x9chearthxe2x80x9d) that is placed on the cooking chamber""s metal floor and sometimes on racks within the cooking chamber; (2) deck ovens designed and manufactured with an incorporated baking chamber floor of a material which serves as a hearth; and (3) custom-built brick ovens which contain a hearth, walls and ceiling of one or more of the above mentioned materials. Food substances that are baked in direct contact with a hearth may be referred to as xe2x80x9cBrick Ovenxe2x80x9d, xe2x80x9cNew York Stylexe2x80x9d, xe2x80x9cNeapolitanxe2x80x9d, or xe2x80x9cOld Worldxe2x80x9d products.
Brick ovens are considered by many bakers to produce a product that is superior to that which can be produced in ovens utilizing a conventional, convection or impingement cooking chamber but lacking a hearth. Most commonly, these ovens employ a primary thermostatically controlled heating means of electricity, natural gas, or propane. In some applications, wood or coal is used. However, temperature within the cooking chamber of a wood or coal fired oven is often difficult to control and preheat times are lengthy. New wood-burning brick ovens, featuring a primary heating means via natural gas, electricity or propane with wood incorporated mainly for its visual appeal, have attempted to remedy this shortcoming.
There are many reasons why a brick oven produces superior baked food substances. Superior quality is generally attributed to the fact that food substances are placed directly on a pre-heated hearth. The hearth also has a tendency to absorb moisture during the baking process due to its porous qualities. Although the food substances are subjected to heat from all sides thereby simultaneously baking from all sides, the most intense and rapid heat transfer takes place from beneath due to the direct contact between the pre-heated hearth and the food substance. This degree of heat transfer can not be achieved in ovens where direct contact with a pre-heated hearth is not possible.
Other technologies that improve heat transfer include hot air convection cooking and forced hot air impingement, which serve to reduce the cold zone that surrounds food substances. These technologies increase the rate at which heat transfer takes place; however, these technologies still fail to achieve the same rapidity of heat transfer that is achieved via the direct contact with a pre-heated hearth.
The rapid heat transfer that takes place between a pre-heated hearth.and food substances results in a reduced bake time and a baking process that effectively causes food substances to bake from the bottom-up. This yields a more crisp, lighter, and puffy crust on baked food substances. Additionally, because any toppings that may be placed on the dough bake more slowly than the crust, there is less opportunity for the toppings to dry out. Liquids contained in toppings also have less opportunity to be absorbed by a slow baking crust which results in a soggy product.
Bakers who utilize brick ovens report the task of baking food substances in brick ovens is far more labor intensive than baking with a common deck oven, as more training is required to achieve satisfactory results than is necessary with the common deck oven. A number of shortcomings were cited which explain the increased difficulty of operation.
One such shortcoming is wide fluctuations in hearth temperature. These fluctuations are caused by the placement of food substances directly on the hearth for baking. When a food substance is placed directly on the hearth, the heat transfer that takes place results in a decrease in the temperature of the hearth. When baking is complete and the food substance is removed, the area of the hearth on which baking occurred must be given time to recover its lost energy and return to optimum baking temperature before another food substance can be placed on the same area and baked with a similar result. This is known as recovery time. This recovery process also serves to purge the hearth of moisture that was absorbed during the baking process. In high volume operations, bakers report difficulty remembering which areas of the hearth are in the process of recovery and which areas have recovered to optimum baking temperature. When multiple bakers are involved in production, this process becomes extremely difficult.
Because the food substances are commonly placed directly on the hearth to achieve rapid heat transfer, there are seldom pans, screens and similar devices utilized in the baking process. Without the use of pans and screens, bakers face additional challenges operating a brick oven. For preparing food substances prior to placement in a brick oven, a baker""s peel or similar device is used. A peel is often made of a material that allows food substances to easily slide across its surface when dusted with flour, corn meal or similar substances. Food substances are slid off of the peel and directly onto the preheated hearth. A similar device is used to free food substances from the hearth and remove them from the oven when baking is complete. Upon removal, an oven broom or similar device is used to sweep flours, corn meals and other residuals from the baking process off of the hearth in preparation for the placement of another food substance. These are time consuming and highly labor intensive processes. Furthermore, due to the lack of leverage afforded by such devices and the dimensions of deep cooking chambers, these devices are usually of considerable length and difficult to manipulate in smaller kitchens. These tasks become more tedious when numerous food substances occupy the cooking chamber(s) at the same time and numerous bakers are involved in the production process.
Brick ovens also share the commonly reported shortfall of common deck ovens which is the necessity of having to open the door to the baking chamber repeatedly to check food substances baking on the hearth. Due to the rapid transfer of heat from the hearth to food substances as well as varying hearth and ambient air temperatures within the cooking chamber, bakers must make regular observations to ensure a quality product. This is especially prevalent in high volume operations that utilize brick ovens with multiple bakers involved in the baking process at the same time. Furthermore, the increased frequency of opening the oven door results in greater temperature fluctuations within the cooking chamber. The result of this extensive interaction is inconsistent product quality, decreased energy efficiency, and an uncomfortable, hot work environment. Increased risk of injury also results from the intensive interaction with the oven. Because the process of checking for doneness of food substances is repeated so often, some brick oven manufacturers have eliminated the oven door. Bakers claim the risk of burns is further increased by the lack of a door due to the direct exposure to the interior cooking chamber while energy efficiency is decreased.
When an operation utilizing a brick oven expands its customer base and experiences increased demand, additional ovens can be added beside or stacked on top of the existing oven if space allows. The stacking of ovens is considered by some bakers to be a less-preferred option as it involves placing the cooking chamber apertures at levels that may not be an optimum access height.
For various examples of brick ovens, see U.S. Pat. No. 6,041,769 to Llodra, Jr. et al; U.S. Pat. No. 5,605,092 to Riccio; U.S. Pat. No. 5,119,719 to DePasquale; and U.S. Pat. No. 4,108,138 to Petin et al., the teachings of all of which are incorporated herein by reference.
Conveyor Ovens
Conveyor ovens are predominantly utilized by higher volume operations which may have had access to greater financial resources when operations were initiated or realized increasing volumes and profitability over time that warranted the increased capital investment that is required to obtain this technology. Conveyor ovens have become the standard production equipment for many commercial bakeries and national food service chains producing food substances such as pizza, flat breads, traditional breads and the like. The conveyor oven""s popularity can be attributed to the fact that it offers increased production volume, consistency, efficiency, safety, and ease of use/operation when compared to other ovens. Bakers utilizing conveyor ovens report the task of producing food substances is significantly less labor intensive, more efficient and requires less training of bakers to achieve consistency. This is due to the conveyor oven""s high degree of automation.
Conveyor ovens employ cooking chambers of various sizes that commonly have interior walls of various types of metal. The size of cooking chambers is often dependent on the designed production capacity as well as the types of food substances to be baked. Horizontal food-grade product conveyors of varying lengths, widths and open areas commonly transport food substances to be baked into, through, and out of the cooking chamber in a continuous motion. These conveyors extend varying lengths from the cooking chamber""s entry and exit apertures to facilitate the loading and unloading of food substances though sometimes they may be fully contained within the cooking chamber. The dimensions of such product conveyors are governed by the dimensions of the cooking chamber and the cooking chamber apertures. Conveyor ovens most commonly employ a primary heating means of electricity, natural gas or propane.
Conveyor ovens offer superior consistency when compared to common deck ovens and brick ovens. The speed at which the product conveyor transports food substances through the cooking chamber is usually adjustable and can be measured in terms of conveyor feet traveled per minute. This allows for precise adjustment of the time food substances undergo the baking process. For example, a conveyor oven employing a baking chamber of 36xe2x80x3 in length with the conveyor speed of one-half of one foot per minute would result in consistent exposure to the baking chamber of exactly six minutes. This results in greater consistency as the baking time in the cooking chamber is not subject to human error. Conveyor oven cooking chambers also maintain more consistent temperatures as they are not subject to dramatic fluctuations caused by the excessive opening and closing of large access doors. Cooking chamber entry and exit apertures are commonly set just large enough to accommodate the food substance. With the incorporation of convection and forced hot air impingement technologies, today""s conveyor ovens efficiently reduce the thin layer of cooler air known as the xe2x80x9ccold zonexe2x80x9d that surrounds foodstuffs in the baking chamber. By reducing the cold zone with convection and impingement technologies, the rate at which heat transfer takes place is improved. When these convection and impingement technologies are combined with a product conveyor that maintains food substances in a continuous state of movement as it transports them through the cooking chamber, inconsistent heat distribution and heat transfer to the food substance are reduced.
Baking food substances in a conveyor oven almost always incorporates the use of pans, screens, and similar devices. This is necessary due to the fact that the food substances are carried through the cooking chamber on a conveyor with varying degrees of open areas. Due to the risk of food substances penetrating the open area of the conveyor which could result in mechanical failure they are seldom or never placed directly on the conveyor. The open area of the conveyor serves to increase the food substances"" exposure to the ambient air and/or infrared heat within the cooking chamber thereby improving heat transfer. The utilization of screens instead of solid pans also allows moisture to be purged from the food substance during the baking process. While this is an improvement over common deck ovens, the rapid heat transfer that takes place between a brick oven""s hearth and a food substance can not be matched. Furthermore, hot air convection and impingement technology has been known to evaporate too much moisture from food substances. As a result, conveyor ovens not only fail to produce the lighter, more crisp and puffy crust that hearth baking is known for but also can produce an excessively dry product.
The latest ovens lacking a product conveyor can not match the level of consistency inherent in a conveyor oven. Timers capable of tracking the exposure of numerous food substances in an oven at once have been installed as standard equipment on various production equipment lacking a product conveyor in an attempt to assist bakers with product consistency. They have also been produced as supplemental systems to be used with equipment lacking timers. In practice, these timers have generally not produced substantial gains in consistency primarily due to human error caused by multiple bakers operating the same ovens at once. During peak production periods, these timers are often turned off by bakers as they are seen as an annoyance. Ironically, while these devices were designed to improve consistency during peak hours when quality control is most difficult to maintain, they are often utilized exclusively during off-peak hours when bakers are involved in other tasks and are more likely to forget about food substances placed in the oven.
When an operation utilizing a conveyor oven expands its customer base and experiences increased demand, additional conveyor ovens can be added beside or stacked on top of the existing oven if space allows. In the case of conveyor ovens, stacking is generally preferred even though this results in a less than optimum access height. Most bakers who utilize conveyor ovens had previously utilized other types of ovens. Bakers who had utilized common deck ovens commented on the increases in consistency, efficiency, and safety offered by conveyor ovens. Bakers who had utilized brick ovens also commented on increases in consistency, efficiency and safety. However, the vast majority of bakers mentioned that while the conversion to a conveyor oven achieves the mentioned benefits, product quality is sacrificed.
For various examples of conveyor ovens, see U.S. Pat. No. 6,157,002 to Schjerven, Sr. et al; U.S. Pat. No. 5,686,004 to Schneider; U.S. Pat. No. 5,881,636 to Sweet et al.; and U.S. Pat. No. 4,739,154 to Bharara et al., the teachings of all of which are incorporated herein by reference.
There is therefore a need for an oven having the speed, efficiency and consistency of a conveyor oven yet able to provide the quality and appeal of a product cooked by a hearth baking process.
A method and apparatus is disclosed for merging the processes of hearth baking and conveyor baking to offer the benefits of the two processes while eliminating many of the shortcomings. In one aspect, the present invention is a horizontal food-grade product conveyor to transport and support food substances within or through a cooking chamber in a continuous motion. The product conveyor assembly comprises a conveyor frame, a support structure, a drive mechanism, and rotatable segments of ceramic, brick, firebrick, stone, baked clay, transite, quarry tile, or other non-metallic material which form an endless baking hearth. Each hearth segment interacts with the next adjacent hearth segment to facilitate turning around a radius while forming and maintaining a continuous, flat product support surface and preheated baking hearth. The continuous flat hearth formed by the segments allows transportation and baking of the food substances in one direction while permitting temperature recovery of the segments during the return travel underneath the formed baking hearth.